1. Field of the Invention
The present invention relates to color matrix screens with colored filters in a triad or delta layout, more particularly large-sized matrix screens, notably matrix screens that are compatible with a television type display.
2. Description of the Prior Art
In a known way, a matrix screen is constituted by two conductive arrays called lines and columns, each intersection of a line and a column forming an image dot or a pixel. To obtain a color display, a mosaic of filters colored red, green and blue is superimposed on these pixels, each filter being before a pixel.
Different layouts may be used to arrange the colored filters so as to obtain the desired color at output. These layouts include notably the triad or delta layout in which the color is obtained by the use of solely red, blue and green pixels arranged in a triangle.
As is shown in FIG. 1, the color matrix screens with colored filters in a triad or delta layout, as manufactured at present, are constituted essentially by a number of parallel lines L1, L2, . . . and by a number of columns C1, C2, C3, C4, C5 . . . , and by pixels P formed at the intersection between the columns C1, C2, . . . and the lines L1, L2, . . . To obtain a color screen, colored filters are associated with each pixel P. Because of their triad or delta layout, the colored filters of the odd lines, namely L1 and L3, are arranged in the sequence blue, red, green, while the colored filters of the even lines L2, . . . are arranged in the sequence green, blue, red. To obtain a triad or delta layout, the even lines have to be offset, in the embodiment shown, by a half pixel, in such a way that the centers of the associated pixels red, green and blue are at the vertices of an isosceles triangle, as represented by the triangle D in FIG. 1. Furthermore, in the context of FIG. 1, an active matrix screen is shown. In this case, the pixels are constituted by electrooptical elements such as a liquid crystal, and they are connected to the corresponding line and column by means of a transistor which is conventionally symbolized by a simple line placed near the intersection of the line conductor and the column conductor considered. These transistors are advantageously thin film transistors (TFTs) and are manufactured in the usual way. As shown in FIG. 1, owing to the offset of the pixels from one line to the next enabling the triad or delta layout to be obtained, the columns are no longer parallel to one another but have to be offset by half a pixel every two lines, as shown in FIG. 1. Consequently, the path of the columns is very important. This raises a number of problems for the addressing, the manufacturing technology and the design. However, a triad or delta arrangement of colored filters provides for an improved reconstruction of the color in the display as compared with other arrangements of colored filters that allow the parallel columns to be kept.
The present invention is therefore aimed at proposing a new structure of colored filters that can be used to have a triad or delta layout while at the same time overcoming the problems encountered in prior art color matrix screens with colored filters in triad or delta layout.